Combined intelligent receive diversity (ird) and mobile transmit diversity (mtd) with independent antenna switching for uplink and downlink

ABSTRACT

Methods and apparatus are provided for allowing a transmitter (Tx) to perform antenna selection independently of a receiver (Rx) in a transceiver supporting both transmit diversity and receive diversity. Certain aspects may utilize a cross switch, which may be used in a parallel or cross configuration, to provide for the independent antenna selection, such that the Rx may maintain the ability to operate on the same antenna as the Tx, on another antenna, or on both antennas for enhanced receive diversity. Furthermore, certain aspects may employ additional switching in the baseband domain in an effort to avoid, or at least reduce, switching glitches in the Rx caused by changing the cross switch configuration. In this manner, the Rx need not re-converge upon antenna switching.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/962,513, entitled “COMBINED INTELLIGENT RECEIVE DIVERSITY (IRD) ANDMOBILE TRANSMIT DIVERSITY (MTD) WITH INDEPENDENT ANTENNA SWITCHING FORUPLINK AND DOWNLINK”, filed Dec. 7, 2010, now allowed, which claims thebenefit of U.S. Provisional Patent Application No. 61/267,650, entitled“DAA: DYNAMIC ANTENNA ALLOCATION”, filed on Dec. 8, 2009, and U.S.Provisional Patent Application No. 61/297,363, entitled “COMBINEDINTELLIGENT RECEIVE DIVERSITY 9IRD) AND MOBILE TRANSMIT DIVERSITY (MTD)FOR INDEPENDENT ANTENNA SWITCHING FOR UPLINK AND DOWNLINK”, filed onJan. 22, 2010, all of which are expressly incorporated by referenceherein in their entirety.

TECHNICAL FIELD

Certain aspects of the present disclosure generally relate to wirelesscommunications and, more particularly, to independent antenna selectionin a user terminal supporting combined receive diversity and transmitdiversity.

BACKGROUND

Wireless communication networks are widely deployed to provide variouscommunication services such as telephony, video, data, messaging,broadcasts, and so on. Such networks, which are usually multiple accessnetworks, support communications for multiple users by sharing theavailable network resources. For example, one network may be a 3G (thethird generation of mobile phone standards and technology) system, whichmay provide network service via any one of various 3G radio accesstechnologies (RATs) including EVDO (Evolution-Data Optimized), 1xRTT (1times Radio Transmission Technology, or simply 1x), W-CDMA (WidebandCode Division Multiple Access), UMTS-TDD (Universal MobileTelecommunications System-Time Division Duplexing), HSPA (High SpeedPacket Access), GPRS (General Packet Radio Service), and EDGE (EnhancedData rates for Global Evolution). The 3G network is a wide area cellulartelephone network that evolved to incorporate high-speed internet accessand video telephony, in addition to voice calls. Furthermore, a 3Gnetwork may be more established and provide larger coverage areas thanother network systems.

A wireless communication network may include a number of base stationsthat can support communication for a number of mobile stations. A mobilestation (MS) may communicate with a base station (BS) via a downlink andan uplink. The downlink (or forward link) refers to the communicationlink from the base station to the mobile station, and the uplink (orreverse link) refers to the communication link from the mobile stationto the base station. A base station may transmit data and controlinformation on the downlink to a mobile station and/or may receive dataand control information on the uplink from the mobile station.

Transceivers with multiple antennas may implement any of varioussuitable diversity schemes in an effort to increase the reliability oftransmitted messages through the use of two or more communicationchannels with different characteristics. Because individual channels mayexperience different levels of interference and fading, such diversityschemes may reduce the effects of co-channel interference and fading, aswell as avoid error bursts.

One type of diversity scheme utilizes space diversity, where a signalmay traverse different propagation paths. In the case of wirelesstransmission, space diversity may be achieved through antenna diversityusing multiple transmitting antennas (transmit diversity) and/ormultiple receiving antennas (receive diversity). By using two or moreantennas, multipath signal distortion may be eliminated, or at leastreduced. In the case of receive diversity with two antennas, the signalfrom the antenna with the least noise (e.g., highest signal-to-noiseratio (SNR)) is typically selected, while the signal from the otherantenna is ignored. Some other techniques use the signals from bothantennas, combining these signals for enhanced receive diversity.

SUMMARY

Certain aspects of the present disclosure generally relate to allowing atransmitter (Tx) to perform antenna selection independently of areceiver (Rx) in a transceiver supporting both transmit diversity andreceive diversity.

Certain aspects of the present disclosure provide a method for wirelesscommunications. The method generally includes selecting a first one offirst and second sets of one or more antennas to connect with a transmitpath, wherein the first and second sets are selectable for both transmitdiversity and receive diversity; transmitting a first signal via atleast one first antenna in the first one of the first and second sets ofantennas; independently selecting a second one of the first and secondsets of antennas to connect with a first receive path, such that theother one of the first and second sets of antennas is connected with asecond receive path; receiving a second signal in the first receive pathvia at least one second antenna in the selected second one of the setsof antennas; and receiving a third signal in the second receive path viaat least one third antenna in the other one of the sets of antennas.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes at least oneprocessor configured to select a first one of first and second sets ofone or more antennas to connect with a transmit path, wherein the firstand second sets are selectable for both transmit diversity and receivediversity; a transmitter configured to transmit a first signal via atleast one first antenna in the first one of the first and second sets ofantennas, wherein the at least one processor is configured toindependently select a second one of the first and second sets ofantennas to connect with a first receive path, such that the other oneof the first and second sets of antennas is connected with a secondreceive path; and a receiver configured to receive a second signal inthe first receive path via at least one second antenna in the selectedsecond one of the sets of antennas and to receive a third signal in thesecond receive path via at least one third antenna in the other one ofthe sets of antennas.

Certain aspects of the present disclosure provide an apparatus forwireless communications The apparatus generally includes means forselecting a first one of first and second sets of one or more antennasto connect with a transmit path, wherein the first and second sets areselectable for both transmit diversity and receive diversity; means fortransmitting a first signal via at least one first antenna in the firstone of the first and second sets of antennas; means for independentlyselecting a second one of the first and second sets of antennas toconnect with a first receive path, such that the other one of the firstand second sets of antennas is connected with a second receive path;means for receiving a second signal in the first receive path via atleast one second antenna in the selected second one of the sets ofantennas; and means for receiving a third signal in the second receivepath via at least one third antenna in the other one of the sets ofantennas.

Certain aspects of the present disclosure provide a computer-programproduct for wireless communications. The computer-program productgenerally includes a computer-readable medium having instructions storedthereon, the instructions being executable by one or more processors.The instructions typically include instructions for selecting a firstone of first and second sets of one or more antennas to connect with atransmit path, wherein the first and second sets are selectable for bothtransmit diversity and receive diversity; instructions for transmittinga first signal via at least one first antenna in the first one of thefirst and second sets of antennas; instructions for independentlyselecting a second one of the first and second sets of antennas toconnect with a first receive path, such that the other one of the firstand second sets of antennas is connected with a second receive path;instructions for receiving a second signal in the first receive path viaat least one second antenna in the selected second one of the sets ofantennas; and instructions for receiving a third signal in the secondreceive path via at least one third antenna in the other one of the setsof antennas.

Certain aspects of the present disclosure provide a method for wirelesscommunications. The method generally includes operating a first receivepath configured to receive signals from a first set of one or moreantennas and process the signals received from the first set ofantennas, wherein a second receive path for receive diversity isconfigured to receive signals from a second set of one or more antennas,wherein the second receive path is deactivated, and wherein the firstset of antennas is different than the second set of antennas; activatingthe deactivated second receive path; determining at least one firstmetric based on signals received in the first receive path and at leastone second metric based on signals received in the activated secondreceive path; if the second metric is better than the first metric,deactivating the first receive path and operating the second receivepath to process the signals received from the second set of antennas;and if the second metric is not better than the first metric,deactivating the second receive path.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes at least oneprocessor configured to operate a first receive path configured toreceive signals from a first set of one or more antennas and process thesignals received from the first set of antennas, wherein a secondreceive path for receive diversity is configured to receive signals froma second set of one or more antennas, wherein the second receive path isdeactivated, and wherein the first set of antennas is different than thesecond set of antennas; to activate the deactivated second receive path;to determine at least one first metric based on signals received in thefirst receive path and at least one second metric based on signalsreceived in the activated second receive path; to deactivate the firstreceive path and operate the second receive path to process the signalsreceived from the second set of antennas, if the second metric is betterthan the first metric; and to deactivate the second receive path if thesecond metric is not better than the first metric.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes means foroperating a first receive path configured to receive signals from afirst set of one or more antennas and process the signals received fromthe first set of antennas, wherein a second receive path for receivediversity is configured to receive signals from a second set of one ormore antennas, wherein the second receive path is deactivated, andwherein the first set of antennas is different than the second set ofantennas; means for activating the deactivated second receive path;means for determining at least one first metric based on signalsreceived in the first receive path and at least one second metric basedon signals received in the activated second receive path; means fordeactivating the first receive path and operating the second receivepath to process the signals received from the second set of antennas, ifthe second metric is better than the first metric; and means fordeactivating the second receive path if the second metric is not betterthan the first metric.

Certain aspects of the present disclosure provide a computer-programproduct for wireless communications. The computer-program productgenerally includes a computer-readable medium having instructions storedthereon, the instructions being executable by one or more processors.The instructions typically include instructions for operating a firstreceive path configured to receive signals from a first set of one ormore antennas and process the signals received from the first set ofantennas, wherein a second receive path for receive diversity isconfigured to receive signals from a second set of one or more antennas,wherein the second receive path is deactivated, and wherein the firstset of antennas is different than the second set of antennas;instructions for activating the deactivated second receive path;instructions for determining at least one first metric based on signalsreceived in the first receive path and at least one second metric basedon signals received in the activated second receive path; instructionsfor deactivating the first receive path and operating the second receivepath to process the signals received from the second set of antennas, ifthe second metric is better than the first metric; and instructions fordeactivating the second receive path if the second metric is not betterthan the first metric.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalaspects of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective aspects.

FIG. 1 illustrates a diagram of a wireless communications network inaccordance with certain aspects of the present disclosure.

FIG. 2 illustrates a block diagram of an example access point (AP) anduser terminals in accordance with certain aspects of the presentdisclosure.

FIG. 3 illustrates example operations for probing different sets ofreceive antennas by activating/deactivating different receive chains forreceive diversity, in accordance with certain aspects of the presentdisclosure.

FIG. 3A illustrates example means for performing the operations of FIG.3.

FIGS. 4-5 illustrate block diagrams of different wireless transceiverfront-end architectures for achieving receive diversity with antennaselection in the front end, in accordance with certain aspects of thepresent disclosure.

FIG. 6 illustrates a block diagram of a wireless transceiver front-endarchitecture for achieving receive diversity with antenna selection inthe baseband, rather than in the front end, in accordance with certainaspects of the present disclosure.

FIG. 7 illustrates a block diagram detailing two receive paths for thetransceiver architecture of FIG. 6 with antenna selection in thebaseband, in accordance with certain aspects of the present disclosure.

FIG. 8 illustrates a block diagram for combining or selecting betweensignals received from a plurality of antennas in the transceiverarchitecture of FIG. 6, in accordance with certain aspects of thepresent disclosure.

FIG. 9 illustrates a block diagram of a wireless transceiver front-endarchitecture for achieving receive diversity, with the architecture ofFIG. 6 replicated to form multiple transceiver channels and aswitchplexer for directing signals between each antenna and one of thethree channels, in accordance with certain aspects of the presentdisclosure.

FIG. 10 illustrates a block diagram of a wireless transceiver front-endarchitecture for achieving transmit diversity, with multiple transceiverchannels and a switchplexer for directing signals between each antennaand one of the three channels, in accordance with certain aspects of thepresent disclosure.

FIG. 11 illustrates a block diagram of a wireless transceiver front-endarchitecture for achieving combined receive and transmit diversity, withthe architecture of FIG. 6 replicated to form multiple transceiverchannels, a cross switch for selecting the antennas in a parallel orcross configuration, and a switchplexer for directing signals betweeneach output of the cross switch and one of the three channels, inaccordance with certain aspects of the present disclosure.

FIG. 12 illustrates a block diagram of the two receive paths for thetransceiver architecture of FIG. 7 with a cross switch added forcombined transmit and receive diversity with independent antennaselection between uplink and downlink, in accordance with certainaspects of the present disclosure.

FIG. 13 illustrates example operations for allowing a transmitter (Tx)to perform antenna selection independently of a receiver (Rx) in atransceiver supporting both transmit diversity and receive diversity, inaccordance with certain aspects of the present disclosure.

FIG. 13A illustrates example means for performing the operations of FIG.13.

DETAILED DESCRIPTION

Various aspects of the present disclosure are described below. It shouldbe apparent that the teachings herein may be embodied in a wide varietyof forms and that any specific structure, function, or both beingdisclosed herein is merely representative. Based on the teachingsherein, one skilled in the art should appreciate that an aspectdisclosed herein may be implemented independently of any other aspectsand that two or more of these aspects may be combined in various ways.For example, an apparatus may be implemented or a method may bepracticed using any number of the aspects set forth herein. In addition,such an apparatus may be implemented or such a method may be practicedusing other structure, functionality, or structure and functionality inaddition to or other than one or more of the aspects set forth herein.Furthermore, an aspect may comprise at least one element of a claim.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother aspects.

The antenna diversity techniques described herein may be used incombination with various wireless technologies such as Code DivisionMultiple Access (CDMA), Orthogonal Frequency Division Multiplexing(OFDM), Time Division Multiple Access (TDMA), Spatial Division MultipleAccess (SDMA), and so on. Multiple user terminals can concurrentlytransmit/receive data via different (1) orthogonal code channels forCDMA, (2) time slots for TDMA, or (3) sub-bands for OFDM. A CDMA systemmay implement IS-2000, IS-95, IS-856, Wideband-CDMA (W-CDMA), or someother standards. An OFDM system may implement Institute of Electricaland Electronics Engineers (IEEE) 802.11, IEEE 802.16, Long TermEvolution (LTE), or some other standards. A TDMA system may implementGSM or some other standards. These various standards are known in theart.

An Example Wireless System

FIG. 1 illustrates a wireless communications system 100 with accesspoints and user terminals. For simplicity, only one access point 110 isshown in FIG. 1. An access point (AP) is generally a fixed station thatcommunicates with the user terminals and may also be referred to as abase station or some other terminology. A user terminal may be fixed ormobile and may also be referred to as a mobile station, a station (STA),a client, a wireless device, or some other terminology. A user terminalmay be a wireless device, such as a cellular phone, a personal digitalassistant (PDA), a handheld device, a wireless modem, a laptop computer,a personal computer, etc.

Access point 110 may communicate with one or more user terminals 120 atany given moment on the downlink and uplink. The downlink (i.e., forwardlink) is the communication link from the access point to the userterminals, and the uplink (i.e., reverse link) is the communication linkfrom the user terminals to the access point. A user terminal may alsocommunicate peer-to-peer with another user terminal. A system controller130 couples to and provides coordination and control for the accesspoints.

System 100 employs multiple transmit and multiple receive antennas fordata transmission on the downlink and uplink. Access point 110 may beequipped with a number N_(ap) of antennas to achieve transmit diversityfor downlink transmissions and/or receive diversity for uplinktransmissions. A set N_(u) of selected user terminals 120 may receivedownlink transmissions and transmit uplink transmissions. Each selecteduser terminal transmits user-specific data to and/or receivesuser-specific data from the access point. In general, each selected userterminal may be equipped with one or multiple antennas (i.e., N_(ut)≧1).The N_(u) selected user terminals can have the same or different numberof antennas.

Wireless system 100 may be a time division duplex (TDD) system or afrequency division duplex (FDD) system. For a TDD system, the downlinkand uplink share the same frequency band. For an FDD system, thedownlink and uplink use different frequency bands. System 100 may alsoutilize a single carrier or multiple carriers for transmission. Eachuser terminal may be equipped with a single antenna (e.g., in order tokeep costs down) or multiple antennas (e.g., where the additional costcan be supported).

FIG. 2 shows a block diagram of access point 110 and two user terminals120 m and 120 x in wireless system 100. Access point 110 is equippedwith N_(ap) antennas 224 a through 224 ap. User terminal 120 m isequipped with N_(ut,m) antennas 252 ma through 252 mu, and user terminal120 x is equipped with N_(ut,x) antennas 252 xa through 252 xu. Accesspoint 110 is a transmitting entity for the downlink and a receivingentity for the uplink. Each user terminal 120 is a transmitting entityfor the uplink and a receiving entity for the downlink. As used herein,a “transmitting entity” is an independently operated apparatus or devicecapable of transmitting data via a frequency channel, and a “receivingentity” is an independently operated apparatus or device capable ofreceiving data via a frequency channel. In the following description,the subscript “dn” denotes the downlink, the subscript “up” denotes theuplink, N_(up) user terminals are selected for simultaneous transmissionon the uplink, N_(dn) user terminals are selected for simultaneoustransmission on the downlink, N_(up) may or may not be equal to N_(dn),and N_(up) and N_(dn) may be static values or can change for eachscheduling interval. Beam-steering or some other spatial processingtechnique may be used at the access point and user terminal.

On the uplink, at each user terminal 120 selected for uplinktransmission, a TX data processor 288 receives traffic data from a datasource 286 and control data from a controller 280. TX data processor 288processes (e.g., encodes, interleaves, and modulates) the traffic data{d_(up)} for the user terminal based on the coding and modulationschemes associated with the rate selected for the user terminal andprovides a data symbol stream {s_(up)} for one of the N_(ut,m) antennas.A transceiver front end (TX/RX) 254 receives and processes (e.g.,converts to analog, amplifies, filters, and frequency upconverts) arespective symbol stream to generate an uplink signal. The transceiverfront end 254 may also route the uplink signal to one of the N_(ut,m)antennas for transmit diversity via an RF switch, for example. Thecontroller 280 may control the routing within the transceiver front end254.

A number N_(up) of user terminals may be scheduled for simultaneoustransmission on the uplink. Each of these user terminals transmits itsset of processed symbol streams on the uplink to the access point.

At access point 110, N_(up) antennas 224 a through 224 ap receive theuplink signals from all N_(up) user terminals transmitting on theuplink. For receive diversity, a transceiver front end 222 may selectsignals received from one of the antennas 224 for processing. Forcertain aspects of the present disclosure, a combination of the signalsreceived from multiple antennas 224 may be combined for enhanced receivediversity. The access point's transceiver front end 222 also performsprocessing complementary to that performed by the user terminal'stransceiver front end 254 and provides a recovered uplink data symbolstream. The recovered uplink data symbol stream is an estimate of a datasymbol stream {s_(up)} transmitted by a user terminal. An RX dataprocessor 242 processes (e.g., demodulates, deinterleaves, and decodes)the recovered uplink data symbol stream in accordance with the rate usedfor that stream to obtain decoded data. The decoded data for each userterminal may be provided to a data sink 244 for storage and/or acontroller 230 for further processing.

On the downlink, at access point 110, a TX data processor 210 receivestraffic data from a data source 208 for N_(dn) user terminals scheduledfor downlink transmission, control data from a controller 230 andpossibly other data from a scheduler 234. The various types of data maybe sent on different transport channels. TX data processor 210 processes(e.g., encodes, interleaves, and modulates) the traffic data for eachuser terminal based on the rate selected for that user terminal TX dataprocessor 210 may provide a downlink data symbol streams for one of moreof the N_(dn) user terminals to be transmitted from one of the N_(ap)antennas. The transceiver front end 222 receives and processes (e.g.,converts to analog, amplifies, filters, and frequency upconverts) thesymbol stream to generate a downlink signal. The transceiver front end222 may also route the downlink signal to one or more of the N_(ap)antennas 224 for transmit diversity via an RF switch, for example. Thecontroller 230 may control the routing within the transceiver front end222.

At each user terminal 120, N_(ut,m) antennas 252 receive the downlinksignals from access point 110. For receive diversity at the userterminal 120, the transceiver front end 254 may select signals receivedfrom one of the antennas 252 for processing. For certain aspects of thepresent disclosure, a combination of the signals received from multipleantennas 252 may be combined for enhanced receive diversity. The userterminal's transceiver front end 254 also performs processingcomplementary to that performed by the access point's transceiver frontend 222 and provides a recovered downlink data symbol stream. An RX dataprocessor 270 processes (e.g., demodulates, deinterleaves, and decodes)the recovered downlink data symbol stream to obtain decoded data for theuser terminal.

Those skilled in the art will recognize the techniques described hereinmay be generally applied in systems utilizing any type of multipleaccess schemes, such as SDMA, OFDMA, CDMA, SDMA, and combinationsthereof.

Example Dynamic Antenna Allocation

FIG. 4 illustrates a block diagram 400 of a wireless transceiverfront-end architecture for achieving receive diversity with antennaselection in the front end. Although only two antennas ANT0 402 ₀ andANT1 402 ₁ are illustrated in FIG. 4 (and other figures), the examplearchitectures provided throughout this disclosure may be expanded tocases involving more than two antennas. A radio frequency (RF) switch404 may select between the antennas 402 for transmitting or receivingsignals. A duplexer 406 (or duplexing assembly) may allow the transmitpath 408 (represented as “Tx”) and the receive path 410 (represented as“Rx”) to share a common antenna 402 selected by the switch 404. As usedherein, a duplexer generally refers to a switching device that permitsbi-directional communication over a single channel through alternate useof the same antenna for both the transmitter and the receiver. Forreception, a received signal output from the duplexer 406 may beamplified by a low noise amplifier (LNA) 412 before being processed bythe remainder of the receive path 410. The front-end architecture ofFIG. 4 also achieves transmit diversity, since the transmit path 408 maytransmit signals on either ANT0 or ANT1.

FIG. 5 illustrates a block diagram 500 of a different wirelesstransceiver front-end architecture for achieving receive diversity withantenna selection in the front end. In FIG. 5, the transmit path 408 maytransmit signals only on ANT0 via a transmit filter 502; the transmitpath has no way to transmit signals on ANT1. The transmit filter 502 maykeep signals received on ANT0 from entering the transmit path and, evenmore importantly, may prevent the transmit path's high-powered signalsfrom interfering with the lower power received signals. Similarly,signals received by the antenna 402 selected by the switch 404 may befiltered by a receive filter 504 before being amplified by the LNA 412for the receive path 410. The receive filter 504 may prevent thetransmit path's high-powered signals from interfering with the lowerpower signals wirelessly received by the antennas 402 and ensure thatonly received signals in the frequency band of interest are processed bythe receive path 410.

The transmit filter 502 and/or the receive filter 504 may be implantedwith a surface acoustic wave (SAW) filter. As defined herein, a SAWfilter generally refers to a semiconductor device that uses thepiezoelectric effect to turn an input electrical signal into mechanicalvibrations that are converted back into electrical signals in thedesired frequency range. In this manner, the SAW filter may filter outundesirable frequencies.

Although the front-end architectures of FIGS. 4 and 5 provide receivediversity, the receive path 410 may experience a discontinuity when thefront end is probing to determine selection between the two antennas402. Furthermore, the RF switch 404 may have an insertion loss ofapproximately 0.5 dB, thereby leading to decreased sensitivity. In thefront-end architecture of FIG. 4, transmission power may be lost if theantenna 402 chosen for increased received SNR has lower efficiency.

Accordingly, what is needed are techniques and apparatus that providefor receive diversity, but overcome the problems and limitations of thefront-end architectures of FIGS. 4 and 5.

FIG. 6 illustrates a block diagram 600 of a wireless transceiverfront-end architecture for achieving receive diversity with antennaselection in the baseband, rather than in the front end. In FIG. 6, anRF switch is not used. Rather, two receive paths 410 ₀, 410 ₁ areemployed. A duplexer 406 allows antenna ANT0 to be shared by thetransmit path 408 and the first receive path 410 ₀ including a first LNA412 ₀. A receive filter 504 may filter out undesirable frequencies in asignal received by antenna ANT1 from reaching the second receive path410 ₁ including a second LNA 412 ₁.

With the front-end architecture of FIG. 6, receive diversity is achievedwith performance gains over the front-end architectures of FIGS. 4 and5. Because there is no switch causing an insertion loss, sensitivity maybe greater than that in the front-end architectures of FIGS. 4 and 5.Moreover, probing of and selection between the receive paths 410 occursin the baseband, so there is no loss of continuity in the processedsignal. In other words, the non-selected receive path may be probedwhile the selected receive path is operating. Also, since selectionoccurs in the baseband, switching glitches may be avoided. By using aparticular receive path 410 only after convergence, there are no probinggaps in reception of the digitally processed signal, which is what ismeant by no loss of continuity (i.e., no reception discontinuity).Finally, the cost of the additional receive path may be negligible,especially when compared to the monetary price of an RF switch and theensuing insertion loss, which sacrifices performance.

FIG. 7 illustrates an example block diagram 700 showing the two receivepaths 410 for the transceiver architecture of FIG. 6 in detail. Afterthe received RF signal has been amplified by the LNA 412, the amplifiedsignal may be mixed with a local oscillator signal (RxLO) 713 by a mixer714, typically to downconvert the signal to an intermediate frequency(IF). The mixed signal may be filtered by an anti-aliasing filter (AAF)716 before being digitized (i.e., converted to the digital domain) by ananalog-to-digital converter (ADC) 718. Digital signal processing mayinclude processing the digitized signal in one or more digital filters(DF) 720, an automatic gain compensation (AGC) block 722, and ademodulator 724 before the received information may be finally extractedfrom the signal received at the antennas 402.

The dashed line 726 may represent a chip boundary, such that blocksbelow the line 726 may be incorporated in one or more integratedcircuits (ICs), while the items above the dashed line 726 may be outsideof the ICs and located on a printed circuit board (PCB) for the userterminal 120 (or access point 110). The dashed line 728 may represent ademarcation between the RF analog domain and the baseband domain, suchthat components above the line 728 operate in the RF domain, while itemsbelow the line 728 operate in the baseband domain.

In operation, one of the receive paths (e.g., 410 ₀) may be the selectedreceive path (i.e., the primary path), and signals received at ANT0 maybe processed through the receive path 410 ₀ in an effort to extractinformation from the received signals. While the selected receive path410 ₀ is operating, the non-selected receive path (e.g., 410 ₁) may bebriefly activated in an effort to probe the signals received at ANT1.This brief activation may occur periodically, repeatedly at non-periodicintervals, or intermittently. However, temporary activation of bothreceive paths is not to be confused with a receive diversity schemeinvolving combining information from the two receive paths 410, althoughthis may be done as another possibility for certain aspects. Rather, thenoise (and/or interference) on each receive path 410 may be measured,and a measure of each receive path's SNR (or SINR) may be calculated.For certain aspects, this calculation may comprise determination of achannel quality indicator (CQI).

If the current selected receive path (i.e., the primary path) 410 ₀ isdeemed to have lower noise (e.g., a higher SNR or better CQI) than thatof the current non-selected path 410 ₁, then the receive path 410 ₀ mayremain activated as the primary path. However, if the currentnon-selected receive path (i.e., the secondary path) 410 ₁ is deemed tohave lower noise (e.g., a higher SNR or better CQI) than that of thecurrent selected path 410 ₀, then the receive path 410 ₀ may bedeactivated, and the former non-selected path 410 ₁ may be activated asthe selected receive path for at least a certain dwelling period (e.g.,10 or more frames). Once this swap occurs, signals received at ANT1 maybe processed through the receive path 410 ₁ in an effort to extractinformation from the received signals, at least until the receive path410 ₀ is once again determined to have lower noise through briefactivation of the non-selected receive path 410 ₀ for probing purposes.

For example, while performing full minimum mean square error (MMSE)receive diversity, separate CQIs may be computed for ANT0 and ANT1. Ifthe CQI for the currently selected receive path is suitable to maintainthe desired performance level, the other receive path may bedeactivated. As another example, while receiving the primary receivedsignal (Prx), the CQI for the diversity received signal (Drx) may alsobe measured. The receive path for the Drx may be selected if the CQI forthe Drx is better than that of the Prx, and the receive path for the Prxmay be subsequently deactivated.

For certain aspects, the SNR (or other metric) of the currentnon-selected receive path may need to be higher than the SNR (or higheror lower than the other corresponding metric, depending on the metric)of the current selected receive path by at least a certain amount (i.e.,a threshold value) before the non-selected receive path is selected asthe new selected receive path in an effort to provide increased systemstability.

During the brief activation of the non-selected receive path, the AGCblock 722, digital filters 720, and other components in the front-endarchitecture may most likely be provided sufficient settling time forthe processed signal to converge before determining the noise on thenon-selected receive path. By waiting to measure the noise until afterconvergence, whenever the current non-selected receive path isconsidered to have lower noise than the current selected receive path,the current non-selected receive path can be safely and immediatelyrelied on as the new selected receive path for exclusive reception. Inthis manner, the receive path swap may occur without any glitches orother loss of continuity. Furthermore, there are no gaps in receptionfor probing purposes.

For certain aspects, the brief activation of non-selected receive pathsmay involve all available antennas or any subset thereof. For certainaspects, the brief activation and probing of the non-selected receivepath(s) may occur while continuing reception on the current selectedreceive path. For certain aspects, the one or more metrics—determinedduring or after probing of the receive paths 410 to make the decision inselecting one of the receive paths for reception—may beperformance-related (e.g., CQI, SNR, signal-to-interference-plus-noiseratio (SINR), bit error rate (BER), block error rate (BLER), non-droppedcall, and/or data rate (throughput)), may be related to the availabilityor cost of resources for the user terminal 120 (e.g., heat or batterypower), may be related to the availability or cost of resources for theaccess point 110 (e.g., downlink transmit power), may be related to theavailability or cost of resources for the network (e.g., networkcapacity), or any combination thereof.

A combination of metrics may yield higher user satisfaction withperformance. For example, energy-aware adaptive activating (ordeactivating) receive diversity (e.g., both receive paths 410 on)increases not just performance, but enhances theperformance-versus-power-consumption tradeoff, which is often moreimportant to users than pure performance by itself.

For certain aspects of the present disclosure, the probing (“sounding”)of candidate sets of antennas for receive diversity may be appropriatelyscheduled during time intervals that do not interfere with anothermeasurement being made by the user terminal (or access point). In otherwords, the probing need not interfere with extraordinary eventsunrelated to the direct business of receiving. For example, the probingmay not be scheduled during Compressed-Mode, inter-RAT (radio accesstechnology) measurements, etc. in UMTS. For instance, Compressed-Modemay most likely be scheduled only when receiving on the primaryantenna(s) (i.e., using receive path 410 ₀.

As illustrated in FIG. 8, each receive path 410 in the transceiverarchitecture of FIG. 6 described above may be associated with one ormore antennas 402. When a single receive path 410 may receive signalsfrom more than one antenna, an RF selector/combiner 802 may connect theantennas 402 with the duplexer 406 or receive filter 504 in the receivepath 410. The selector/combiner 802 may function to select between oneof the antennas 402 for reception or may combine the received RF signalsfrom multiple antennas, in an effort to obtain extra diversity.

For example, while the transceiver is operating with selected receivepath 410 ₀, the non-selected receive path 410 ₁ may be probed (bymeasuring one or more metrics such as noise as described above) usingone or more of various possible configurations of the antennas 402_(1,a), 402 _(1,b) associated with this receive path. For example themetric(s) may be measured with signals received by only antenna 402_(1,a), then with signals received by only antenna 402 _(1,b), and thenwith signals received from both antennas 402 _(1,a), 402 _(1,b) combinedby the selector/combiner 802. Then, if the metric (e.g., SNR) of thenon-selected receive path 410 ₁ for any of the three configurations ofantennas 402 _(1,a), 402 _(1,b) is better than the antenna configurationbeing used (or, for certain aspects, all possible antennaconfigurations) on the current selected receive path 410 ₀, then thenon-selected receive path 410 ₁ may become the new selected receive pathfor exclusive reception with one of the three possible configurations ofantennas 402 _(1,a), 402 _(1,b), most likely the antenna configurationyielding the best metric(s).

FIG. 3 illustrates example operations 300 for probing different sets ofreceive antennas by activating/deactivating different receive chains forreceive diversity. The operations 300 may be performed, for example, bya user terminal 120 or an access point 110. The operations 300 maybegin, at 302, by operating a first receive path (e.g., receive path 410₀) configured to receive signals from a first set of one or moreantennas (e.g., the three antennas 402 coupled to the first receive path410 ₀ in FIG. 8) and process the signals received from the first set ofantennas. The second receive path (e.g., receive path 410 ₁) for receivediversity may be configured to receive signals from a second set of oneor more antennas (e.g., antennas 402 _(1,a), 402 _(1,b)). At 302, thesecond receive path may be deactivated. The first set of antennas isdifferent than the second set of antennas.

At 304, the second receive path may be deactivated. At 306, at least onefirst metric may be determined based on signals received in the firstreceive path, and at least one second metric may be determined based onsignals received in the activated second receive path.

If the second metric is better than the first metric (e.g., the secondSNR is higher than the first SNR) at 308, the first receive path may bedeactivated at 310, and the second receive path may be operated toprocess the signals received from the second set of antennas. If thesecond metric is not better than the first metric, however, the secondpath may be deactivated at 314.

For certain aspects, at least one third metric may be determined basedon a combination of signals received in the first and second receivepaths. If the third metric is better than the first and the secondmetrics, the first and the second receive paths may be operated toprocess the signals received from the first and second sets of antennas.If the third metric is not better than the first and the second metrics,however, the second receive path may be deactivated.

An Example Combined IRD and MTD with Independent Antenna Switching forUplink and Downlink

Expanding upon the transceiver architecture of FIG. 6, FIG. 9illustrates a block diagram 900 of a wireless transceiver front-endarchitecture for achieving receive diversity, with the architecture ofFIG. 6 replicated to form multiple transceiver channels 902 and aswitchplexer 904 for directing signals between each antenna 402 and oneof the channels 902. Although two antennas 402 and three transceiverchannels 902 are illustrated in FIG. 9, the ideas described herein maybe expanded to any number of antennas and any number of transceiverchannels. Furthermore, for some aspects, the switches internal to theswitchplexer 904 may move together to select among different transceiverchannels 902, while for other aspects, the switches may moveindependently such that different receive paths 410, rather thandifferent channels 902, may be selected. FIG. 9 also illustrates a poweramplifier (PA) 906 in each of the transmit paths 408 for amplifying asignal to be transmitted via ANT0. Section 908 may represent the circuitblocks within one or more ICs, while section 910 may representcomponents residing outside of the ICs, such as circuits disposed on aprinted circuit board (PCB).

In FIG. 9, the transmit paths 408 may only transmit signals on ANT0, sothere is no transmit diversity with respect to the antennas. However,signals received on either ANT0 or ANT1 may be processed by the variousreceive paths 410, thereby providing receive diversity. For example,signals received on ANT0 may be processed by one of the three receivepaths 410 ₀, whereas signals received on ANT1 may be processed by one ofthe three receive paths 410 ₁.

FIG. 10 illustrates a block diagram 1000 of a wireless transceiverfront-end architecture for achieving transmit diversity, with multipletransceiver channels 1002 and a switchplexer 904 for directing signalsbetween each antenna and one of the three channels. For each transceiverchannel 1002 in FIG. 10, a switch 1004 (e.g., a single-pole,double-throw (SPDT) switch) may select one of two duplexers 406 throughwhich the output signal generated by the power amplifier (PA) 906 may besent via the switchplexer 904 to one of the antennas ANT0 or ANT1. Inthis manner, transmit diversity may be achieved. However, since eachreceive path 410 may only receive signals from a single antenna, thearchitecture of FIG. 10 does not achieve receive diversity with respectto antenna selection.

In the wireless transceiver front-end architectures described abovewith, as well as in conventional front-end architectures with antennadiversity, switching between antennas typically forces the receive pathto switch every time the transmit path switches, or vice versa. However,receive path (Rx) performance (e.g., based on SINR) is not necessarilymaximized where transmit path (Tx) performance is, and vice versa. Byselecting an antenna for best performance in the transmit path, receivepath performance may suffer, or vice versa. Moreover, by switchingbetween one antenna for receive and another antenna for transmit,switching glitches may most likely be introduced into at least thereceive path.

Accordingly, what is needed are techniques and apparatus for independentantenna selection between transmitting and receiving (e.g., betweenuplink and downlink transmissions). Ideally, such solutions would workin transceivers with combined receive diversity and transmit diversityand would not introduce any switching glitches.

FIG. 11 illustrates a block diagram 1100 of a wireless transceiverfront-end architecture for achieving combined receive and transmitdiversity with independent antenna selection for transmitting andreceiving. The architecture in FIG. 11 is similar to the architecture inFIG. 9, but with the addition of a cross switch 1102 between theantennas 402 and the switchplexer 904.

The cross switch 1102 may switch between a parallel (=) or a cross (X)configuration between the four contact points. Although only fourcontact points are shown for a cross switch linking two antennas to a2-input switchplexer (or two independent switchplexers) as an example,the ideas described herein may be expanded to other cross switchconfigurations. When the cross switch 1102 is in the parallelconfiguration, ANT0 may be coupled to the duplexer 406, the transmitpath 408, and the receive path 410 ₀ in each transceiver channel 902,and ANT1 may be coupled to the receive filter 504 and the receive path410 ₁ in each transceiver channel 902. When the cross switch 1102 is inthe cross configuration, ANT1 may be coupled to the duplexer 406, thetransmit path 408, and the receive path 410 ₀ in each transceiverchannel 902, and ANT0 may be coupled to the receive filter 504 and thereceive path 410 ₁ in each transceiver channel 902.

With the cross switch 1102, the transmit path 408 may transmit signalson either ANT0 (parallel configuration) or ANT1 (cross configuration),thereby achieving transmit diversity. Furthermore, the receive path 410₀ may receive signals on either ANT0 (parallel configuration) or ANT1(cross configuration), thereby achieving receive diversity. Likewise,the receive path 410 ₁ may receive signals on either ANT1 (parallelconfiguration) or ANT0 (cross configuration), thereby also achievingreceive diversity. Accordingly, the front-end architecture in FIG. 11supports both transmit diversity (more specifically, antenna switchedtransmit diversity) and receive diversity, and the antenna fortransmitting (e.g., for uplink) may be selected independently of theantenna for receiving (e.g., for downlink). Furthermore, the receiver(including both receive paths 410 ₀ and 410 ₁ for at least onetransceiver channel 902) may operate on the same antenna as thetransmitter (e.g., the transmit path 408 for at least one transceiverchannel 902), on an antenna different from the transmitter, or on bothantennas, combining the signals received on both antennas for enhancedreceive diversity.

To avoid, or at least reduce, any switching glitches when switchingbetween configurations of the cross switch 1102, switching of the signalmay also occur between the two receive paths 410 ₀, 410 ₁ in thebaseband domain after digitization. For example, the modem software orfirmware may handle this corresponding additional (nearly) simultaneousbaseband switching, which may allow a particular newly selected receivepath to converge before messages are read from this particular receivepath. Before converging, the messages may be read from the previouslyselected receive path. As used herein, converging generally refers tothe baseband processing loops (e.g., the channel estimation loop, a timetracking loop, or a frequency tracking loop) having settled or reached asteady state condition.

As an example, FIG. 12 illustrates a block diagram 1200 of the tworeceive paths for the transceiver architecture of FIG. 7 with a crossswitch 1102 added for combined transmit and receive diversity withindependent antenna selection between uplink and downlink, in accordancewith certain aspects of the present disclosure. Another way to view FIG.12 is to consider the block diagram 1200 as illustrating a singletransceiver channel 902 from FIG. 11 without a switchplexer 904.

Prior to the reception shown in FIG. 12, the cross switch 1102 was inthe parallel configuration, such that the receive path 410 ₀ may havebeen receiving signals from ANT0 and the receive path 410 ₁ may havebeen receiving signals from ANT1 during transmissions from the transmitpath 408 via ANT0. After the cross switch 1102 is switched to the crossconfiguration as shown in FIG. 12, signals received by ANT0 may bedigitized by the ADC 718 ₁ after being routed to the receive filter 504,amplified by the LNA 412 ₁, mixed with the local oscillator 714 ₁, andfiltered by the anti-alias filter 716 ₁.

Because the remaining components in the digital baseband domain forreceive path 410 ₁ may not have yet converged, the digitized signal fromreceive path 410 ₁ may be processed by the digital filter 720 ₀ andother components from receive path 410 ₀. These other components mayinclude a compensation block 1202 ₀ and a variable gain amplifier (VGA)1204 ₀ associated with the AGC block 722 ₀. The compensation block 1202may process CORDIC (COordinate Rotation DIgital Computer) algorithms andadjust IQ imbalance, DC offset, and the like. The processed results fromthe VGA 1204 ₀ may be stored in a sample RAM 1206 ₁ (or other type ofmemory buffer) for receive path 410 ₁. Once the components in thedigital baseband domain have converged in receive path 410 ₁ for signalsreceived on ANT0, then the digitized signal may be processed by thedigital filter 720 ₁ and other subsequent components from receive path410 ₁.

As described above, this baseband switching may be controlled by themodem firmware or software. By handling the switching glitch in thebaseband, certain aspects of the present disclosure may provide seamlesstransitioning from one antenna to another when changing theconfiguration of the cross switch. In other words, received signalcontinuity may be ensured without any performance loss that would likelyoccur if the receive path had to re-converge.

FIG. 13 illustrates example operations 1300 that may be performed, forexample, by a wireless transceiver in a user terminal 120 or an accesspoint 110, for allowing a transmitter (Tx) to perform antenna selectionindependently of a receiver (Rx) in a transceiver supporting bothtransmit diversity and receive diversity. The operations 1300 may begin,at 1302, by selecting a first one of first and second sets of one ormore antennas to connect with a transmit path, wherein the first andsecond sets are selectable for both transmit diversity and receivediversity. At 1304, the transceiver may transmit a first signal via atleast one first antenna in the first one of the first and second sets ofantennas selectable for both (antenna switched) transmit diversity andreceive diversity.

At 1306, the transceiver may independently select a second one of thefirst and second sets of antennas, such that the other one of the firstand second sets of antennas is connected with a second receive path. At1308, the transceiver may receive a second signal in the first receivepath via at least one second antenna in the selected second one of thesets of antennas. The transceiver may receive, at 1310, a third signalin the second receive path via at least one third antenna in the otherone of the sets of antennas.

The various operations or methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrate circuit (ASIC), or processor. Generally,where there are operations illustrated in Figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering. For example, blocks 1302 to 1310 in FIG. 13correspond to blocks 1302A to 1310A illustrated in FIG. 13A.

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

As used herein, the phrase “at least one of A or B” is meant to includeany combination of A and B. In other words, “at least one of A or B”comprises the following sets: [A], [B] and [A, B].

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array signal (FPGA) or other programmable logic device(PLD), discrete gate or transistor logic, discrete hardware componentsor any combination thereof designed to perform the functions describedherein. A general purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thepresent disclosure may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in any form of storage medium that is knownin the art. Some examples of storage media that may be used includerandom access memory (RAM), read only memory (ROM), flash memory, EPROMmemory, EEPROM memory, registers, a hard disk, a removable disk, aCD-ROM and so forth. A software module may comprise a singleinstruction, or many instructions, and may be distributed over severaldifferent code segments, among different programs, and across multiplestorage media. A storage medium may be coupled to a processor such thatthe processor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

The functions described may be implemented in hardware, software,firmware or any combination thereof. If implemented in software, thefunctions may be stored as one or more instructions on acomputer-readable medium. A storage media may be any available mediathat can be accessed by a computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers.

Thus, certain aspects may comprise a computer-program product forperforming the operations presented herein. For example, such acomputer-program product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For certain aspects, the computer-program product may includepackaging material.

Software or instructions may also be transmitted over a transmissionmedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition oftransmission medium.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

The techniques provided herein may be utilized in a variety ofapplications. For certain aspects, the techniques presented herein maybe incorporated in an access point station, an access terminal, a mobilehandset, or other type of wireless device with processing logic andelements to perform the techniques provided herein.

While the foregoing is directed to aspects of the present disclosure,other and further aspects of the disclosure may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A method for wireless communications, comprising: operating a firstreceive path configured to receive signals from a first set of one ormore antennas and process the signals received from the first set ofantennas, wherein a second receive path for receive diversity isconfigured to receive signals from a second set of one or more antennas,wherein the second receive path is deactivated, and wherein the firstset of antennas is different than the second set of antennas; activatingthe deactivated second receive path; determining at least one firstmetric based on signals received in the first receive path and at leastone second metric based on signals received in the activated secondreceive path; if the second metric is better than the first metric,deactivating the first receive path and operating the second receivepath to process the signals received from the second set of antennas;and if the second metric is not better than the first metric,deactivating the second receive path.
 2. The method of claim 1, furthercomprising: determining at least one third metric based on a combinationof signals received in the first and second receive paths; if the thirdmetric is better than the first and the second metrics, operating thefirst and the second receive paths to process the signals received fromthe first and second sets of antennas; and if the third metric is notbetter than the first and the second metrics, deactivating the secondreceive path.
 3. The method of claim 1, wherein operating the secondreceive path comprises processing the signals received in the secondreceive path without a reception discontinuity between operating thefirst receive path and operating the second receive path.
 4. The methodof claim 1, wherein activating the deactivated second receive pathcomprises activating the deactivated second receive path while operatingthe first receive path.
 5. The method of claim 1, wherein activating ordeactivating the first or the second receive path occurs in the basebandsuch that switching glitches are avoided.
 6. The method of claim 1,wherein determining the at least one first metric and the at least onesecond metric comprises determining the at least one first metric basedon noise and/or interference of the signals received in the firstreceive path and the at least one second metric based on noise and/orinterference of the signals received in the activated second receivepath.
 7. The method of claim 1, wherein the at least one first metric orthe at least one second metric comprises at least one of a channelquality indicator (CQI), a signal-to-noise ratio (SNR), asignal-to-interference-plus-noise ratio (SINR), a bit error rate (BER),a block error rate (BLER), a data rate, battery power, heat, a downlinktransmit power, network capacity, or any combination thereof.
 8. Themethod of claim 1, wherein the at least one first metric and the atleast one second metric are the same type of metric.
 9. The method ofclaim 1, wherein the first receive path is configured to receive thesignals from the first set of antennas via a duplexer coupled to atransmit path.
 10. The method of claim 1, wherein the second set ofantennas comprises a first antenna and a second antenna such thatdetermining the second metric comprises at least one of: determining thesecond metric based on the signals received from the first antenna;determining the second metric based on the signals received from thesecond antenna; and determining the second metric based on a combinationof the signals received from the first and second antennas.
 11. Themethod of claim 1, further comprising: after operating the secondreceive path for a dwelling period, deactivating the second receivepath; and activating the deactivated first receive path before an end ofthe dwelling period.
 12. The method of claim 1, further comprising:activating the deactivated first receive path; determining at least onethird metric based on signals received in the activated first receivepath and at least one fourth metric based on signals received in thesecond receive path; if the third metric is better than the fourthmetric, deactivating the second receive path and operating the firstreceive path to process the signals received from the first set ofantennas; and if the third metric is not better than the fourth metric,deactivating the first receive path.
 13. The method of claim 1, whereindeactivating the first receive path and operating the second receivepath comprises deactivating the first receive path and operating thesecond receive path to process the signals received from the second setof antennas if the second metric is better than the first metric by athreshold value, and wherein deactivating the second receive pathcomprises deactivating the second receive path if the second metric isnot better than the first metric by the threshold value.
 14. The methodof claim 1, further comprising repeating activating the second receivepath, determining the at least one second metric and the at least onefirst metric, and deactivating the second receive path if the secondmetric is not better than the first metric.
 15. The method of claim 1,wherein activating the second receive path comprises activating thesecond receive path during an interval that will not interfere withanother measurement.
 16. The method of claim 1, further comprising:selecting between the first set of antennas and the second set ofantennas, wherein the first and second sets are selectable for bothreceive diversity and antenna switched transmit diversity; andtransmitting a signal via the selected set of antennas.
 17. The methodof claim 16, wherein selecting between the first and second sets ofantennas comprises selecting between configurations of a cross switch,wherein the configurations comprise a parallel configuration and a crossconfiguration.
 18. The method of claim 17, wherein the parallelconfiguration of the cross switch connects the first set of antennaswith the first receive path and the second set of antennas with thesecond receive path and wherein the cross configuration connects thefirst set of antennas with the second receive path and the second set ofantennas with the first receive path.
 19. An apparatus for wirelesscommunications, comprising: at least one processor configured to:operate a first receive path configured to receive signals from a firstset of one or more antennas and process the signals received from thefirst set of antennas, wherein a second receive path for receivediversity is configured to receive signals from a second set of one ormore antennas, wherein the second receive path is deactivated, andwherein the first set of antennas is different than the second set ofantennas; activate the deactivated second receive path; determine atleast one first metric based on signals received in the first receivepath and at least one second metric based on signals received in theactivated second receive path; deactivate the first receive path andoperate the second receive path to process the signals received from thesecond set of antennas, if the second metric is better than the firstmetric; and deactivate the second receive path if the second metric isnot better than the first metric.
 20. The apparatus of claim 19, whereinthe at least one processor is configured to: determine at least onethird metric based on a combination of signals received in the first andsecond receive paths; operate the first and the second receive paths toprocess the signals received from the first and second sets of antennas,if the third metric is better than the first and the second metrics; anddeactivate the second receive path if the third metric is not betterthan the first and the second metrics.
 21. The apparatus of claim 19,wherein the at least one processor is configured to operate the secondreceive path by processing the signals received in the second receivepath without a reception discontinuity between operating the firstreceive path and operating the second receive path.
 22. The apparatus ofclaim 19, wherein the at least one processor is configured to activatethe deactivated second receive path by activating the deactivated secondreceive path while operating the first receive path.
 23. The apparatusof claim 19, wherein the at least one processor is configured toactivate or deactivate the first or the second receive path in thebaseband such that switching glitches are avoided.
 24. The apparatus ofclaim 19, wherein the at least one processor is configured to determinethe at least one first metric and the at least one second metric bydetermining the at least one first metric based on noise and/orinterference of the signals received in the first receive path and theat least one second metric based on noise and/or interference of thesignals received in the activated second receive path.
 25. The apparatusof claim 19, wherein the at least one first metric or the at least onesecond metric comprises at least one of a channel quality indicator(CQI), a signal-to-noise ratio (SNR), asignal-to-interference-plus-noise ratio (SINR), a bit error rate (BER),a block error rate (BLER), a data rate, battery power, heat, a downlinktransmit power, network capacity, or any combination thereof.
 26. Theapparatus of claim 19, wherein the at least one first metric and the atleast one second metric are the same type of metric.
 27. The apparatusof claim 19, wherein the first receive path is configured to receive thesignals from the first set of antennas via a duplexer coupled to atransmit path.
 28. The apparatus of claim 19, wherein the second set ofantennas comprises a first antenna and a second antenna such that the atleast one processor is configured to determine the second metric by atleast one of: determining the second metric based on the signalsreceived from the first antenna; determining the second metric based onthe signals received from the second antenna; and determining the secondmetric based on a combination of the signals received from the first andsecond antennas.
 29. The apparatus of claim 19, wherein the at least oneprocessor is configured to: deactivate, after operating the secondreceive path for a dwelling period, the second receive path; andactivate the deactivated first receive path before an end of thedwelling period.
 30. The apparatus of claim 19, wherein the at least oneprocessor is configured to: activate the deactivated first receive path;determine at least one third metric based on signals received in theactivated first receive path and at least one fourth metric based onsignals received in the second receive path; deactivate the secondreceive path and operate the first receive path to process the signalsreceived from the first set of antennas, if the third metric is betterthan the fourth metric; and deactivate the first receive path if thethird metric is not better than the fourth metric.
 31. The apparatus ofclaim 19, wherein the at least one processor is configured to deactivatethe first receive path and operate the second receive path bydeactivating the first receive path and operating the second receivepath to process the signals received from the second set of antennas ifthe second metric is better than the first metric by a threshold value,and wherein the at least one processor is configured to deactivate thesecond receive path by deactivating the second receive path if thesecond metric is not better than the first metric by the thresholdvalue.
 32. The apparatus of claim 19, wherein the at least one processoris configured to repeat activating the second receive path, determiningthe at least one second metric and the at least one first metric, anddeactivating the second receive path if the second metric is not betterthan the first metric.
 33. The apparatus of claim 19, wherein the atleast one processor is configured to activate the second receive path byactivating the second receive path during an interval that will notinterfere with another measurement.
 34. The apparatus of claim 19,further comprising a transmitter, wherein the at least one processor isconfigured to select between the first set of antennas and the secondset of antennas, wherein the first and second sets are selectable forboth receive diversity and antenna switched transmit diversity, andwherein the transmitter is configured to transmit a signal via theselected set of antennas.
 35. The apparatus of claim 34, wherein the atleast one processor is configured to select between the first and secondsets of antennas by selecting between configurations of a cross switch,wherein the configurations comprise a parallel configuration and a crossconfiguration.
 36. The apparatus of claim 35, wherein the parallelconfiguration of the cross switch connects the first set of antennaswith the first receive path and the second set of antennas with thesecond receive path and wherein the cross configuration connects thefirst set of antennas with the second receive path and the second set ofantennas with the first receive path.
 37. An apparatus for wirelesscommunications, comprising: means for operating a first receive pathconfigured to receive signals from a first set of one or more antennasand process the signals received from the first set of antennas, whereina second receive path for receive diversity is configured to receivesignals from a second set of one or more antennas, wherein the secondreceive path is deactivated, and wherein the first set of antennas isdifferent than the second set of antennas; means for activating thedeactivated second receive path; means for determining at least onefirst metric based on signals received in the first receive path and atleast one second metric based on signals received in the activatedsecond receive path; means for deactivating the first receive path andoperating the second receive path to process the signals received fromthe second set of antennas, if the second metric is better than thefirst metric; and means for deactivating the second receive path if thesecond metric is not better than the first metric.
 38. The apparatus ofclaim 37, further comprising: means for determining at least one thirdmetric based on a combination of signals received in the first andsecond receive paths; means for operating the first and the secondreceive paths to process the signals received from the first and secondsets of antennas, if the third metric is better than the first and thesecond metrics; and means for deactivating the second receive path ifthe third metric is not better than the first and the second metrics.39. The apparatus of claim 37, wherein the means for operating thesecond receive path is configured to process the signals received in thesecond receive path without a reception discontinuity between operatingthe first receive path and operating the second receive path.
 40. Theapparatus of claim 37, wherein the means for activating the deactivatedsecond receive path is configured to activate the deactivated secondreceive path while operating the first receive path.
 41. The apparatusof claim 37, wherein the means for activating or deactivating the firstor the second receive path operates in the baseband such that switchingglitches are avoided.
 42. The apparatus of claim 37, wherein the meansfor determining the at least one first metric and the at least onesecond metric is configured to determine the at least one first metricbased on noise and/or interference of the signals received in the firstreceive path and the at least one second metric based on noise and/orinterference of the signals received in the activated second receivepath.
 43. The apparatus of claim 37, wherein the at least one firstmetric or the at least one second metric comprises at least one of achannel quality indicator (CQI), a signal-to-noise ratio (SNR), asignal-to-interference-plus-noise ratio (SINR), a bit error rate (BER),a block error rate (BLER), a data rate, battery power, heat, a downlinktransmit power, network capacity, or any combination thereof.
 44. Theapparatus of claim 37, wherein the at least one first metric and the atleast one second metric are the same type of metric.
 45. The apparatusof claim 37, wherein the first receive path is configured to receive thesignals from the first set of antennas via a duplexer coupled to atransmit path.
 46. The apparatus of claim 37, wherein the second set ofantennas comprises a first antenna and a second antenna such that themeans for determining the second metric is configured to determine thesecond metric by at least one of: determining the second metric based onthe signals received from the first antenna; determining the secondmetric based on the signals received from the second antenna; anddetermining the second metric based on a combination of the signalsreceived from the first and second antennas.
 47. The apparatus of claim37, further comprising: means for deactivating the second receive pathafter operating the second receive path for a dwelling period; and meansfor activating the deactivated first receive path before an end of thedwelling period.
 48. The apparatus of claim 37, further comprising:means for activating the deactivated first receive path; means fordetermining at least one third metric based on signals received in theactivated first receive path and at least one fourth metric based onsignals received in the second receive path; means for deactivating thesecond receive path and operating the first receive path to process thesignals received from the first set of antennas, if the third metric isbetter than the fourth metric; and means for deactivating the firstreceive path if the third metric is not better than the fourth metric.49. The apparatus of claim 37, wherein the means for deactivating thefirst receive path and operating the second receive path is configuredto deactivate the first receive path and operate the second receive pathto process the signals received from the second set of antennas if thesecond metric is better than the first metric by a threshold value, andwherein the means for deactivating the second receive path is configuredto deactivate the second receive path if the second metric is not betterthan the first metric by the threshold value.
 50. The apparatus of claim37, further comprising means for repeating activating the second receivepath, determining the at least one second metric and the at least onefirst metric, and deactivating the second receive path if the secondmetric is not better than the first metric.
 51. The apparatus of claim37, wherein the means for activating the second receive path isconfigured to activate the second receive path during an interval thatwill not interfere with another measurement.
 52. The apparatus of claim37, further comprising: means for selecting between the first set ofantennas and the second set of antennas, wherein the first and secondsets are selectable for both receive diversity and antenna switchedtransmit diversity; and means for transmitting a signal via the selectedset of antennas.
 53. The apparatus of claim 52, wherein the means forselecting between the first and second sets of antennas is configured toselect between configurations of a cross switch, wherein theconfigurations comprise a parallel configuration and a crossconfiguration.
 54. The apparatus of claim 53, wherein the parallelconfiguration of the cross switch connects the first set of antennaswith the first receive path and the second set of antennas with thesecond receive path and wherein the cross configuration connects thefirst set of antennas with the second receive path and the second set ofantennas with the first receive path.
 55. A computer-program product forwireless communication, comprising a computer-readable medium havinginstructions stored thereon, the instructions being executable by one ormore processors and the instructions comprising: instructions foroperating a first receive path configured to receive signals from afirst set of one or more antennas and process the signals received fromthe first set of antennas, wherein a second receive path for receivediversity is configured to receive signals from a second set of one ormore antennas, wherein the second receive path is deactivated, andwherein the first set of antennas is different than the second set ofantennas; instructions for activating the deactivated second receivepath; instructions for determining at least one first metric based onsignals received in the first receive path and at least one secondmetric based on signals received in the activated second receive path;instructions for deactivating the first receive path and operating thesecond receive path to process the signals received from the second setof antennas, if the second metric is better than the first metric; andinstructions for deactivating the second receive path if the secondmetric is not better than the first metric.
 56. The computer-programproduct of claim 55, further comprising: instructions for determining atleast one third metric based on a combination of signals received in thefirst and second receive paths; instructions for operating the first andthe second receive paths to process the signals received from the firstand second sets of antennas, if the third metric is better than thefirst and the second metrics; and instructions for deactivating thesecond receive path if the third metric is not better than the first andthe second metrics.
 57. The computer-program product of claim 55,wherein operating the second receive path comprises processing thesignals received in the second receive path without a receptiondiscontinuity between operating the first receive path and operating thesecond receive path.
 58. The computer-program product of claim 55,wherein activating the deactivated second receive path comprisesactivating the deactivated second receive path while operating the firstreceive path.
 59. The computer-program product of claim 55, whereinactivating or deactivating the first or the second receive path occursin the baseband such that switching glitches are avoided.
 60. Thecomputer-program product of claim 55, wherein determining the at leastone first metric and the at least one second metric comprisesdetermining the at least one first metric based on noise and/orinterference of the signals received in the first receive path and theat least one second metric based on noise and/or interference of thesignals received in the activated second receive path.
 61. Thecomputer-program product of claim 55, wherein the at least one firstmetric or the at least one second metric comprises at least one of achannel quality indicator (CQI), a signal-to-noise ratio (SNR), asignal-to-interference-plus-noise ratio (SINR), a bit error rate (BER),a block error rate (BLER), a data rate, battery power, heat, a downlinktransmit power, network capacity, or any combination thereof.
 62. Thecomputer-program product of claim 55, wherein the at least one firstmetric and the at least one second metric are the same type of metric.63. The computer-program product of claim 55, wherein the first receivepath is configured to receive the signals from the first set of antennasvia a duplexer coupled to a transmit path.
 64. The computer-programproduct of claim 55, wherein the second set of antennas comprises afirst antenna and a second antenna such that determining the secondmetric comprises at least one of: determining the second metric based onthe signals received from the first antenna; determining the secondmetric based on the signals received from the second antenna; anddetermining the second metric based on a combination of the signalsreceived from the first and second antennas.
 65. The computer-programproduct of claim 55, wherein the computer-readable medium comprises:instructions for deactivating the second receive path after operatingthe second receive path for a dwelling period; and instructions foractivating the deactivated first receive path before an end of thedwelling period.
 66. The computer-program product of claim 55, whereinthe computer-readable medium comprises: instructions for activating thedeactivated first receive path; instructions for determining at leastone third metric based on signals received in the activated firstreceive path and at least one fourth metric based on signals received inthe second receive path; instructions for deactivating the secondreceive path and operating the first receive path to process the signalsreceived from the first set of antennas, if the third metric is betterthan the fourth metric; and instructions for deactivating the firstreceive path if the third metric is not better than the fourth metric.67. The computer-program product of claim 55, wherein deactivating thefirst receive path and operating the second receive path comprisesdeactivating the first receive path and operating the second receivepath to process the signals received from the second set of antennas ifthe second metric is better than the first metric by a threshold value,and wherein deactivating the second receive path comprises deactivatingthe second receive path if the second metric is not better than thefirst metric by the threshold value.
 68. The computer-program product ofclaim 55, further comprising instructions for repeating activating thesecond receive path, determining the at least one second metric and theat least one first metric, and deactivating the second receive path ifthe second metric is not better than the first metric.
 69. Thecomputer-program product of claim 55, wherein activating the secondreceive path comprises activating the second receive path during aninterval that will not interfere with another measurement.
 70. Thecomputer-program product of claim 55, wherein the computer-readablemedium comprises: instructions for selecting between the first set ofantennas and the second set of antennas, wherein the first and secondsets are selectable for both receive diversity and antenna switchedtransmit diversity; and instructions for transmitting a signal via theselected set of antennas.
 71. The computer-program product of claim 70,wherein selecting between the first and second sets of antennascomprises selecting between configurations of a cross switch, whereinthe configurations comprise a parallel configuration and a crossconfiguration.
 72. The computer-program product of claim 71, wherein theparallel configuration of the cross switch connects the first set ofantennas with the first receive path and the second set of antennas withthe second receive path and wherein the cross configuration connects thefirst set of antennas with the second receive path and the second set ofantennas with the first receive path.